package org.apache.lucene.codecs.lucene40;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.codecs.FieldInfosFormat;
import org.apache.lucene.codecs.FieldInfosReader;
import org.apache.lucene.codecs.FieldInfosWriter;
import org.apache.lucene.index.DocValues; // javadoc
import org.apache.lucene.index.DocValues.Type; // javadoc
import org.apache.lucene.store.DataOutput; // javadoc

/**
 * Lucene 4.0 Field Infos format.
 * <p>
 * <p>Field names are stored in the field info file, with suffix <tt>.fnm</tt>.</p>
 * <p>FieldInfos (.fnm) --&gt; Header,FieldsCount, &lt;FieldName,FieldNumber,
 * FieldBits,DocValuesBits,Attributes&gt; <sup>FieldsCount</sup></p>
 * <p>Data types:
 * <ul>
 *   <li>Header --&gt; {@link CodecUtil#checkHeader CodecHeader}</li>
 *   <li>FieldsCount --&gt; {@link DataOutput#writeVInt VInt}</li>
 *   <li>FieldName --&gt; {@link DataOutput#writeString String}</li>
 *   <li>FieldBits, DocValuesBits --&gt; {@link DataOutput#writeByte Byte}</li>
 *   <li>FieldNumber --&gt; {@link DataOutput#writeInt VInt}</li>
 *   <li>Attributes --&gt; {@link DataOutput#writeStringStringMap Map&lt;String,String&gt;}</li>
 * </ul>
 * </p>
 * Field Descriptions:
 * <ul>
 *   <li>FieldsCount: the number of fields in this file.</li>
 *   <li>FieldName: name of the field as a UTF-8 String.</li>
 *   <li>FieldNumber: the field's number. Note that unlike previous versions of
 *       Lucene, the fields are not numbered implicitly by their order in the
 *       file, instead explicitly.</li>
 *   <li>FieldBits: a byte containing field options.
 *       <ul>
 *         <li>The low-order bit is one for indexed fields, and zero for non-indexed
 *             fields.</li>
 *         <li>The second lowest-order bit is one for fields that have term vectors
 *             stored, and zero for fields without term vectors.</li>
 *         <li>If the third lowest order-bit is set (0x4), offsets are stored into
 *             the postings list in addition to positions.</li>
 *         <li>Fourth bit is unused.</li>
 *         <li>If the fifth lowest-order bit is set (0x10), norms are omitted for the
 *             indexed field.</li>
 *         <li>If the sixth lowest-order bit is set (0x20), payloads are stored for the
 *             indexed field.</li>
 *         <li>If the seventh lowest-order bit is set (0x40), term frequencies and
 *             positions omitted for the indexed field.</li>
 *         <li>If the eighth lowest-order bit is set (0x80), positions are omitted for the
 *             indexed field.</li>
 *       </ul>
 *    </li>
 *    <li>DocValuesBits: a byte containing per-document value types. The type
 *        recorded as two four-bit integers, with the high-order bits representing
 *        <code>norms</code> options, and the low-order bits representing 
 *        {@link DocValues} options. Each four-bit integer can be decoded as such:
 *        <ul>
 *          <li>0: no DocValues for this field.</li>
 *          <li>1: variable-width signed integers. ({@link Type#VAR_INTS VAR_INTS})</li>
 *          <li>2: 32-bit floating point values. ({@link Type#FLOAT_32 FLOAT_32})</li>
 *          <li>3: 64-bit floating point values. ({@link Type#FLOAT_64 FLOAT_64})</li>
 *          <li>4: fixed-length byte array values. ({@link Type#BYTES_FIXED_STRAIGHT BYTES_FIXED_STRAIGHT})</li>
 *          <li>5: fixed-length dereferenced byte array values. ({@link Type#BYTES_FIXED_DEREF BYTES_FIXED_DEREF})</li>
 *          <li>6: variable-length byte array values. ({@link Type#BYTES_VAR_STRAIGHT BYTES_VAR_STRAIGHT})</li>
 *          <li>7: variable-length dereferenced byte array values. ({@link Type#BYTES_VAR_DEREF BYTES_VAR_DEREF})</li>
 *          <li>8: 16-bit signed integers. ({@link Type#FIXED_INTS_16 FIXED_INTS_16})</li>
 *          <li>9: 32-bit signed integers. ({@link Type#FIXED_INTS_32 FIXED_INTS_32})</li>
 *          <li>10: 64-bit signed integers. ({@link Type#FIXED_INTS_64 FIXED_INTS_64})</li>
 *          <li>11: 8-bit signed integers. ({@link Type#FIXED_INTS_8 FIXED_INTS_8})</li>
 *          <li>12: fixed-length sorted byte array values. ({@link Type#BYTES_FIXED_SORTED BYTES_FIXED_SORTED})</li>
 *          <li>13: variable-length sorted byte array values. ({@link Type#BYTES_VAR_SORTED BYTES_VAR_SORTED})</li>
 *        </ul>
 *    </li>
 *    <li>Attributes: a key-value map of codec-private attributes.</li>
 * </ul>
 *
 * @lucene.experimental
 */
public class Lucene40FieldInfosFormat extends FieldInfosFormat {
  private final FieldInfosReader reader = new Lucene40FieldInfosReader();
  private final FieldInfosWriter writer = new Lucene40FieldInfosWriter();
  
  /** Sole constructor. */
  public Lucene40FieldInfosFormat() {
  }

  @Override
  public FieldInfosReader getFieldInfosReader() throws IOException {
    return reader;
  }

  @Override
  public FieldInfosWriter getFieldInfosWriter() throws IOException {
    return writer;
  }
}
